New Brunswick

PotashCorp reveals plans to flood Penobsquis mine

The Department of Environment has released PotashCorp's plans to decommission and flood its original Penobsquis mine.

Mine will be allowed to fill with brine already leaking into the site

Potashcorp is seeking permission to flood its original Penobsquis mine.

The Department of Environment and Local Government has released PotashCorp's plans to decommission and flood its original Penobsquis mine.

Potash mining on the site ended in November and salt production operations ended there in January.

PotashCorp also shut down the brand new Picadilly mine across the street in January.

If the plan is approved, the pumping of salt water (brine) that is already leaking into the mine will be slowed, allowing the facility to fill in a controlled manner.

"The mass amount of brine flowing into and being removed from the mine will be carefully balanced and monitored daily," according to an environmental impact assessment document filed with the province by PotashCorp consultant, Amec Foster Wheeler.

A PotashCorp spokesman says the mine will flood "naturally" over a period of 18 months. (Amec Foster Wheeler)

The document says some mining equipment will remain underground.

"Equipment left in the underground mine, such as vehicles, will have batteries removed, be drained of petroleum, oil and and lubricant products."

The number of vehicles involved is not revealed.

"We are conducting an inventory of what's there and will decide on what can be removed and/or reused after that," said PotashCorp spokesman Randy Burton.

Once the flooding begins, it is expected to take about 18 months for the mine to fill.

After that surface buildings, including the mine headframes, will be demolished.

The entire process is expected to be completed by 2022.

Water quality to be monitored

The document goes on to say that throughout the process groundwater levels, and water quality in the Penobsquis area, will be monitored through four drilled wells.

Existing domestic wells will also be monitored, although not the wells at homes and farms in the area that dried up in the years after leaking at the mine began.

Tanker trucks line up, waiting to be filled with salt brine from the potash mine. (CBC)
Those homes have been hooked into a municipal type water system and in most cases their wells have been filled with cement.

Brine leaking began at the mine in 1998 and controlling it has become an industry on its own, with constant pumping required to allow mine operations to continue.

The rate of leakage has been controlled by a continuous process of grouting — essentially forcing a cement-like material into openings in the mine wall.

Despite those efforts, brine leaches in at a rate of 4500 litres per minute.

Some is removed via a pipeline to a site near Cassidy Lake and from there to on to the Bay of Fundy through a second pipeline.

The remainder is taken by tanker trucks to Saint John where it is released into Courtenay Bay.

There are 43 drivers involved in the brine trucking, who make as many as 100 trips per day.

The flooding of the mine cannot begin without the go-ahead from New Brunswick's environment department.

"Significant negative residual effects are not anticipated," the report concludes.